The present invention relates to a coolant circulating apparatus for supplying coolant to a heat load in a circulating manner and more specifically to a coolant circulating apparatus with an automatically recovering mechanism in which the coolant filling the heat load and outside piping can be recovered automatically when operation is completed, in maintenance and inspection, and the like.
In this type of coolant circulating apparatus, in general, the coolant at an adjusted temperature is housed in a tank and supplied by a pump to the heat load in a circulating manner to thereby cool the heat load. The coolant the temperature of which rises due to cooling of the heat load and which flows back into the tank exchanges heat with a refrigerant in a heat exchanger to thereby adjust the temperature.
If such a coolant circulating apparatus is used for a treating process of a semiconductor, for example, very expensive completely fluorinated liquid is used as the coolant. Therefore, if an amount of coolant to be used is large, an initial cost becomes high. Therefore, it is desired to efficiently cool the heat load by using as small an amount of coolant as possible.
The heat load is normally connected to the circulating apparatus through outside piping prepared by a user. A kind, a heat capacity, a disposition place, and the like of the heat load are not necessarily the same at all times and are different in various manners depending on users. Therefore, a length, a diameter, and the like of outside piping are also different. The larger the length and the diameter of outside piping, the larger a volumetric capacity of the heat load including the outside piping becomes and the more a liquid level in the tank lowers when operation of the circulating apparatus starts to supply the coolant to the outside piping and the heat load. Therefore, if an amount of coolant housed in the tank is merely reduced, the liquid level in the tank may lower to hinder operation of the pump.
On the other hand, although it is preferable to recover all the coolant filling the heat load and outside piping into the tank when the operation of the coolant circulating apparatus is completed or at the time of maintenance, inspection, or the like, there has not been proposed means for easily, efficiently, and automatically recovering the coolant in the heat load and the outside piping. In recovering the coolant in this manner, the liquid level in the tank may rise and the coolant may overflow due to recovery of the coolant if the coolant of such an amount that a proper liquid level is obtained in an operating state has been housed in the tank. Therefore, it is necessary to prevent the liquid level from rising too much in recovery.
It is an object of the present invention to provide an economical and rational coolant circulating apparatus with an automatically recovering mechanism, the apparatus being able to be handled easily. In the apparatus, a heat load can be cooled efficiently by using a small amount of coolant, the coolant in the heat load and outside piping can be easily, efficiently, and automatically recovered and a liquid level in the tank does not change substantially in circulation of the coolant to the heat load and recovery of the coolant from the heat load.
To achieve the above object, a coolant circulating apparatus of the present invention comprises: a hermetically sealed tank in which a coolant at a controlled temperature is housed; a heat load connected to the tank through a feed pipe and a return pipe; a pump for supplying the coolant in the tank to the heat load through the feed pipe and the return pipe in a circulating manner; a liquid level regulating chamber communicating through a bottom portion thereof with an inside of the tank; a compressed gas supply source for supplying compressed gas; a liquid level regulating gas duct including a duct connecting the compressed gas supply source and the liquid level regulating chamber and a solenoid valve connected in the duct to regulate a liquid level of the coolant in the tank by causing the coolant to flow out into the tank from the liquid level regulating chamber or to flow into the liquid level regulating chamber from the tank by switching the solenoid valve to supply or discharge the compressed gas to and from the liquid level regulating chamber; a recovery gas duct including a duct connecting the compressed gas supply source and the feed pipe and a solenoid valve connected in the duct to cause the coolant building up in the feed pipe, the heat load, and the return pipe to flow back into the tank by switching the solenoid valve to supply the compressed gas to the feed pipe; a solenoid valve connected to a vapor phase portion of the tank to open the vapor phase portion to an outside in regulation of the liquid level of the coolant; a level switch provided in the tank to detect the liquid level of the coolant; a flowmeter connected to the return pipe to detect a flow rate of the coolant flowing in the return pipe; and a controller for controlling the pump and the respective solenoid valves.
It is preferable that the liquid level regulating chamber is disposed in the tank to occupy a part of a space in which the coolant is housed. It is preferable that a volumetric capacity of the liquid level regulating chamber is such a size that the coolant in the feed pipe, the heat load, and the return pipe can be housed in the liquid level regulating chamber.
In the circulating apparatus of the invention having the above structure, the liquid level of the coolant in the tank lowers when the coolant in the tank flows from the feed pipe into the heat load and the return pipe due to a start of operation of the apparatus and the liquid level of the coolant in the tank rises when the coolant filling the feed pipe, the heat load, and the return pipe is recovered into the tank after the operation is completed. Therefore, during the operation, the compressed gas from the compressed gas supply source is supplied into the liquid level regulating chamber through the liquid level regulating gas duct and the coolant in the liquid level regulating chamber is pushed out into the tank to thereby make up the reduction of coolant to maintain the liquid level at a height which does not hinder the operation of the pump. In recovery of the coolant, the compressed gas in the liquid level regulating chamber is discharged to cause a part of the coolant in the tank to flow into the liquid level regulating chamber to thereby absorb a rise of the liquid level in the tank. As a result, it is possible to efficiently cool the heat load while absorbing and regulating changes of the liquid level when the operation starts or in recovery by the liquid level regulating chamber by using a small amount of coolant.
The recovery of the coolant is carried out by supplying the compressed gas to the feed pipe through the recovery gas duct and pressing the coolant building up from the feed pipe in the heat load and the return pipe into the tank with the compressed gas.
By controlling by opening and closing the solenoid valves connected to the liquid level regulating gas duct and the recovery gas duct with the controller to automatically carry out the regulation of the liquid level and the recovery of the coolant synchronously, it is possible to easily, efficiently, and automatically recover the coolant in the heat load and the piping.